1. Field of the Invention
The present invention relates to an image processing method that may be adopted to remove noise contained in an image.
2. Description of Related Art
The smoothing technologies adopted for noise removal in the related art include noise removal filters referred to as edge-preserving smoothing filters that assure adaptive smoothing with edge structures retained intact by comparing the noise fluctuation width with a differential value representing the difference between pixels. Such edge-preserving smoothing filters include the ε filter disclosed in non-patent reference 1, the σ filter disclosed in non-patent reference 2, the bilateral filter disclosed in non-patent reference 3 and the trilateral filter disclosed in non-patent reference 4, the latter two of which assure higher levels of performance.
Nonpatent reference 1: H. Harashima et al., “ε-Separating Nonlinear Digital Filter and Its Application”, The Transactions of the Institute of Electronics, Information and Communication Engineers, April/1982 issue, vol. J65-A No. 4, pp. 297-304
Nonpatent reference 2: J. S. Lee, “Digital Image Smoothing and the Sigma Filter”, Computer Vision, Graphics and Image Processing, vol. 24, pp. 255-269, 1983
Nonpatent reference 3: C. Tomasi et al., “Bilateral Filtering for Gray and Color Images” Proceedings of the 1998 IEEE International Conference on Computer Vision, Bombay, India
Nonpatent reference 4: Prasun Choudhury et al., “The Trilateral Filter for High Contrast Images and Meshes”, Eurographics Symposium on Rendering 2003, pp. 1-11